Portable power saw



n Sept. 2

F. J. NANKIVELL PORTABLE POWER SAW 1922 2 Shee1.s-8heet l Filed Feb. 16

gm SM10/MO@ Sept Z, 924.,

F. J. NANKIVELL PORTABLE POWER SAW Filed Feb. 16, 1922 2 Sheets-Sheet 2 The metal block `13, Figure 5, serves as a bearing for the shaft 4 and screw 12 is threaded in it. Block 13 is secured tothe casing 8 by the screws 14.

I have found that a portable saw, which is notv rigidly held to a stationary frame, must run at a 4low speed to be successfully operated and to protect the operator. Furthermore, in order that the complete outfit be light, it is necessary that the motor be of the high speed type. It is, therefore, necessary to have a very large reduction in speed from that of the motor to that of the saw. This I achieve by the use of the worm drive in which the ratio of reduction may be as high as 300 to 1. v

I have also found that it is important to have a comparatively large-number of points of support for the saw and that these supports must not be complicated. The use of the equalizing levers 7 and 16 provide a simple and effective arrangement that takes care of inequalities or deformations, due either to wear or temperature changes, in the saw blade the two sets of rollers on each side of the point of application of the work moving only about their pivots, whilel the other sets of rollers can yield radially as well as rock about their pivots.

I am aware that rimsaws have been con-l structed with single rollers yieldingly mounted and also that such saws have been di'ivenby means of gears acting on the periphery; but such prior constructions have not proved to be of long life and economical.

It is to be noted that my portable saw can be operated in any position, but, as a large proportion of the work is done with the ai'- ticle to be sawed below the operator, I have found my construction, wherein the centre of gravity of the saw is below the operators grip on the frame, of great advantage.

I claim 1. A portable saw comprising in combination, an annular saw blade formed with spaced radial slots, and a motor driven worm directly meshing with said radial slots;

2. A portable saw comprising in combination, an annular saw blade formed with spaced radial slots, and a motor driven worm arranged tangential to said blade and directly meshing with said radial slots.

3. A portable saw comprisingin combination an .annular saw blade having its outer ed to said shaft. i f

pitch equal to the spacing of and engaging in the said radial slots, a shaft vin said worin gear and a high speed motor direct connect- 4. A portable saw comprising in combination an annular saw blade formed with radial slots, a casing surrounding said blade for the major part of its circumference, guides carried by said casing for said blade,

a motor mountedupon said casing with,its vshaft in tangential relation to said blade, and a worm upon said motor shaft directlyY meshing with said radial slots.

. 5. A portable saw comprising in combination an annulai` sawblade having its outer edge provided with teeth, a, casing surrounding said blade for the vmajor part of its circumference, pins mounted in' said casing at a plurality of points, equalizing levers pivoting upon said pins, and grooved rollers Arotatably mounted on said equalizing levers,

one at each end thereof, and contacting with the inner edge of the annular saw.

6. A portable sawcomprising in combination Aan annular saw blade, a sheath surrounding said saw blade throughout the major portion of its periphery, pivots'r tion an annular saw blade, a sheath surrounding said' saw` blade throughout the major portion of its periphery and having a gap for the reception of the materia-l to be sawed, pivotsymounted in said sheath, equalizing levers mounted on said pivots, grooved rollers rotatably ymounted on said equalizing levers and contacting with the inner edge'of the annular saw blade, two of said equalizing levers being mounted upon said sheath adj acentto said gap for pivotal movement only, and a plurality of said equalizing levers being mounted in spaced rela-tion upon said sheath for both pivotal and radial movement, and means for` driving said blade.- v

' FRANK J. NANKrvELL. 

